The global smartphone market contracted for the first time in Q4 2017, according to Gartner. About 408 million smartphones were shipped during the quarter, representing a decline of 5.6% from Q4 2016.

With worldwide smartphone sales sliding in the quarter, the two leading market players — Samsung and Apple — faced smartphone unit declines. Samsung's smartphone sales fell over 3% in Q4, while sales of Apple's iPhones slipped 5%, according to Gartner. However, Apple said in its earnings that global iPhone sales only fell 1%. The decline during the holiday quarter is especially notable because consumers typically receive new phones during the holiday season.

The average smartphone life cycle is lengthening. Consumers often postpone smartphone upgrades because they're buying more high-quality models, according to Gartner Research Director Anshul Gupta. As the technological gap between device generations decreases — meaning that older models are often very capable of handling the majority of the primary utilities smartphones afford — consumers are less inclined to upgrade since their existing smartphone satisfies their needs. Lengthening upgrade cycles can negatively affect brands and businesses looking to utilize new and innovative app features aimed at increasing consumer engagement.

There's a lack of high-quality, low-cost smartphones. The limited availability of quality, affordable smartphones is preventing some consumers from making the leap from feature phones to smartphones. Furthermore, feature phone makers continue to add more functionality to their phones, making them a more appealing option. For instance, Google is adding support for its voice assistant, Google Assistant, to feature phones, starting with Reliance Jio's JioPhone.

But global smartphone shipments will likely pick up again in 2018, albeit slightly. Wider adoption of AI-infused voice assistants, virtual and augmented reality experiences, and smarter cameras by phone makers could encourage consumers to upgrade their devices sooner, and propel feature phone users to make the shift to smartphones. This will also help bolster the app developer market. That's because new-phone users tend to re-download their favorite and most-used apps, upgrade apps they haven't updated in a while, and try new apps, particularly those that take advantage of new technological capabilities in newer devices.